how to get the inside function from a composite function

Question

b) In order to express the function P=√(19t^6-1) as a composition of two functions the outer of which is a root function,
we would let u be equal to the inner function, u= 
and then write P as a function of u, as follows: P=

(c) In order to express the function w=−10ln(5r+10) as a composition of two functions the outer of which is a logarithmic function,
we would let u be equal to the inner function, u= 
and then write ww as a function of u, as follows: w=

 

PLEASE HELP

 

Answer 1

b).  let u = 19t⁶-1  P(u) = √u

 

c).  let u = 5r+10  w(u)= -10lnu